The present invention relates to a circuit arrangement.
Circuit arrangements can be regarded as electric or electronic circuits implemented on a particular structure, e.g. on a printed circuit board, a single-chip module (SCM) or a multi-chip module (MCM). A circuit arrangement is a sandwiched structure which comprises signal layers that are sandwiched between ground and voltage layers.
In more complex circuit arrangements, e.g. on circuit boards for computer systems, there is a need to supply the circuit arrangement with more than two voltage levels as represented by the nominal supply voltage and ground, so that very often, a third voltage level or even more voltage levels must be implemented on a circuit board. The voltage layers may therefore relate to different potentials with respect to ground. The nominal supply voltage is very often denoted as VDD, and the other above mentioned third voltage level is often denoted as V3. For example, the ground voltage can be at 0 Volt, VDD can be at 1.8 Volt, and V3 can be set to 1.5 Volt.
The voltage layers, also referred to in the following as power layers, might consist of a layer of electrically conductive material. A special kind of voltage layer is the ground layer which is at a potential of 0 Volt. In contrast to the voltage and ground layers, the signal layers of a circuit board comprise signal wires that are used to carry high-frequency electric currents. A signal via corresponds to one or more signal wires that run in essence perpendicular to the sandwiched layer structure and that connect wires of different signal planes. If a signal via penetrates a voltage plane or a ground plane, a so called void or anti-pad is generated to avoid shorting the signal carried by the signal via to the ground or power plane.
US published application 2007/0111576 A1 discloses a circuit on a printed circuit board comprising wiring dedicated to supply electric board components which comprises at least three different reference planes characterized by capacitance provided for a given signal wiring in a discontinuity section, wherein the discontinuity causes a broken high-frequency return path of the current signal wiring, and wherein the capacitance is formed by a voltage island placed within a signal layer located next to the given signal wiring.
The voltage islands placed within a signal layer has the disadvantage that they impact the wiring capabilities of the circuit boards or circuit cards, especially in space limited areas. The usage of voltage islands within circuit boards or within circuits comprised on circuit boards is therefore not generally applicable.